The present invention is related to suspension systems and specifically to a suspension control unit incorporated in a vehicle computer controlled suspension system and to the fluid control unit and valves incorporated in the suspension control unit.
Computer controlled suspension systems use a computer to control the damping provided by each of the suspension system actuators. Typically, computer suspension systems incorporate actuators on to which are mounted electrically adjustable valves which are driven by computer to control the flow of hydraulic fluid the actuators and thus control the damping provided by the actuators.
Virtually all of these computer suspension control systems on the market use orifice controlled flow valves to regulate damping forces. There are several reasons why orifice control has become the de-facto standard. One reason is that conventional shock absorbers have always used orifice control technology, and as such orifice controlled technology is better understood and more easily adapted to computer control. Another reason is that traditional and commonly accepted feedback control theory is better implemented with orifice control techniques. Moreover, orifice control valves can be considerably smaller than the constant force (pressure regulating) valves. Furthermore, constant force valves incorporated in computer control systems, in principle, result in very harsh and totally unacceptable performance. Use of constant force valves in computer controlled suspension systems has required in many instances the use of bulky and expensive accumulators to smooth abrupt force transitions that occur with the operation of the constant force pressure regulating valves. However, orifice control valves are not capable of being constantly and very rapidly adjusted as a wheel of the vehicle coupled to a corresponding actuator moves so as to provide for optimum damping.
As such, a suspension control system is desirable that is not subject to the problems of orifice controlled valves, and which incorporates valves that are not susceptible to the adjustment limitations and instabilities of current control valves.